Card-Programmed Calculator

Card-Programmed Calculator

This assembly of early electronic equipment is
the IBM Card-Programmed Electronic Calculator
(CPC). Announced on May 20, 1949, the new machine
was "capable of handling problems of a sequential
nature, in which a long series of arithmetical
steps must be performed to obtain a single solution."
Although designed to be particularly useful for
evaluating long engineering formulas, the CPC
later was used for large accounting applications
as well.

The new system consisted of an IBM 604 Electronic
Calculator (third from left), with its Type 521
card punch (to its right), a Type 402 or 417 accounting
machine (second from left) and an optional Type
941 auxiliary storage unit (extreme left). The
402, which had been announced in July 1948 along
with the 604, was an improved successor to the
IBM 405 accounting machine. An optional version
of the 402 -- the Type 417 -- came without alphabetic
printing. Both the 402 and 417 read 150 cards
a minute; the 417 printed 150 lines per minute
and the 402 printed 100 cards a minute. Both of
them, and the 604 and 521 punch, could be used
as separate machines if desired. The 941, also
announced in May 1949, was built from components
used in an electromechanical calculator, and provided
greater memory capacity for the CPC.

In the CPC configuration shown here, the 604
operated as a slave to the 402. The desired operations
-- addition, subtraction, multiplication, division,
and other procedures, such as square root -- could
be wired on the 604's plugboard and called for
by instructions in punched cards read in the 402.

The IBM punched cards used in any operation were
fed into the 402 accounting machine. That unit
recorded in printed form any of the data punched
in the card, thereby supplying a record of the
operation. Data from the card could be accumulated
or relayed to the other CPC units for calculation,
for punching into another card or for retention
until later in the calculation. The 402 also printed
the results of any steps in the operation.

Additions or subtractions of factors relayed
to the 604 were performed at speeds in excess
of 2,000 a second, while multiplications or divisions
were processed at 86 a second. The results were
recorded in punched cards by the 521 card punch,
relayed to the accounting machine or to the 941
storage unit for subsequent use in the operation.

More than 600 CPCs were produced in the early-1950s
before they were overtaken by advancements incorporated
into the IBM 700 series of electronic computers.
(VV2198)